Change-speed planetary transmission

ABSTRACT

A four-speed transmission having an over drive is disclosed which comprises two basic planetary gearsets and one dual intermeshed planet pinion planetary gearset and three clutches and two brakes. The construction and arrangement is such that an appropriate reduction ratio is provided for each of forward speeds without causing rotary members between input and output shaft to rotate faster than the input and output shafts.

BACKGROUND OF THE INVENTION

The present invention relates to change-speed transmissions for motor vehicles which are driven by a prime mover through a torque converter or a fluid coupling.

Although a variety of four-speed transmissions including an over drive have thus far been proposed, they have the following disadvantages:

(1) If gear ratio for the fourth speed (overdrive) is selected at an appropriate value, gear ratios for the first, second and third speeds will become remote from practical optimum values and vice versa.

(2) There is a rotary element which will rotate faster than an input shaft or an output shaft during frequently used operation range from the first speed to the fourth speed, so that a shaft rotatably journaling the rotary element will be overloaded and high speed rotation of the rotary element will cause a rattle.

Automotive vehicles installed with an automatic transmission are generally worse in fuel economy than their counterparts installed with a manual transmission. To solve this disadvantage of automatic transmissions, an automatic transmission having an over drive is proposed. A conventional automatic four-speed transmission with an over drive has a disadvantage that the gear ratio for a particular speed is not suitable for automotive vehicles. Another disadvantage is that there is a rotary element which rotates far faster than an input shaft.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a change-speed transmission which has an over drive and provides gear ratios suitable for all speeds, respectively.

It is another object of the present invention to provide a change-speed transmission of the above character which includes a plurality of planetary gearsets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an upper half of a first preferred embodiment of a four-speed transmission according to the present invention;

FIG. 2 is a front end view of a representative example of a basic planetary gearset incorporated in FIG. 1;

FIG. 3 is a front end view of a representative example of a dual intermeshed planet pinion planetary gearset incorporated in FIG. 1;

FIG. 4 is a schematic view of a second preferred embodiment of a four-speed transmission according to the present invention; and

FIG. 5 is a schematic view of a third preferred embodiment of a four-speed transmission according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The transmission schematically illustrated in FIG. 1 includes a first basic planetary gear set 10 and a second basic planetary gear set 12 (see FIG. 2). Gearset 10 includes a ring gear R₁, a sun gear S₁, a carrier C₁ and planet pinions 14 journaled rotatably upon the carrier C₁. Gearset 12 includes a ring gear R₂, a sun gear S₂, a carrier C₂ and planet pinions 16 which are journaled rotatably upon the carrier C₂.

Sun gears S₁ and S₂ are splined to or connected to a hollow shaft 18 for simultaneous rotation therewith. If desired, the sun gears S₁ and S₂ may be formed as a common sun gear.

A dual intermeshed planet pinion planetary gearset 20 includes a ring gear R₃, a sun gear S₃, a carrier C₃, planet pinion shafts 22 fixed to the carrier C₃ and planet pinions 24 journaled rotatably upon shafts 22 so that they mesh with the sun gear S₃ (see also FIG. 3). Pinions 24 mesh with other pinions 26 which also are journaled by means of pinion shafts 28 fixed to the carrier C₃. Pinions 26 mesh with the ring gear R₃. It will be noted that the second basic planetary gearset 12 is located between the first basic planetary gearset 10 and dual intermeshed planet pinion planetary gearset 20.

Carriers C₁ and C₃ are splined to or connected to a hollow shaft 30 extending through the hollow shaft 18 for simultaneous rotation therewith. If desired, the carriers C₁ and C₃ may be formed as a common carrier.

Ring gear R₃ is connected to carrier C₂ for simultaneous rotation therewith.

An input shaft 32 extends through hollow shaft 30. Sun gear S₃ is connected to or splined to the input shaft 32 for simultaneous rotation therewith. The input shaft 32 is driven by an engine through a torque converter or fluid coupling, although not shown.

An output shaft 34 is axially aligned with the input shaft 32. Ring gear R₂ is splined to or connected to the output shaft 34 for simultaneous rotation therewith.

A first clutch K₁ is provided and adapted to engage the input shaft 32 with shaft 18. A second clutch K₂ is provided and adapted to engage the input shaft 32 with ring gear R₁. A third clutch K₃ is provided and adapted to engage ring gear R₁ with shaft 18.

A first brake B₁ is provided and adapted to anchor shaft 18. A second brake B₂ is provided and adapted to anchor carrier C₂ and ring gear R₃.

From the preceding statement and FIG. 1 it will be noted that planetary gear sets 10, 12 and 20 are arranged concentrically about shaft 32.

The gearing is controlled in the following manner:

1st Speed

For first speed, the clutch K₃ is engaged and the brake B₂ applied and a power is transmitted from the sun gear S₃ to output shaft 34 through carrier C₃, carrier C₁, sun gear S₁, shaft 18 sun gear S₂ and ring gear R₂. Under this condition, since ring gear R₃ is held stationary or braked by brake B₂, carrier C₃ rotates in the opposite direction to a direction of rotation of sun gear S₃ (or input shaft 32) at a reduced speed. This reduced rotation of the carrier C₃ is transmitted to carrier C₁ through shaft 30. Since ring gear R₁ and sun gear S₁ are locked by clutch K₃, first planetary gearset 10 rotates as a unit. Sun gear S₂ rotates as sun gear S₁ does through shaft 18. Since carrier C₂ is held stationary by brake B₂, ring gear R₂ rotates in the opposite direction to a direction of rotation of sun gear S₂ at a reduced speed. This reduced rotation of ring gear R₂ is transmitted to output shaft 34. It will be noted that rotation of output shaft 34 is in the same direction as input shaft 32, but at a reduced speed.

From the preceding statement, it will be apparent that there is no rotary element which will rotate faster than input shaft 32.

2nd Speed

For second speed, the clutch K₃ is engaged and the brake B₁ applied and a power is transmitted from sun gear S₃ to output shaft 34 through, ring gear R₃, carrier C₂, and ring gear R₂ because carrier C₃ and sun gear S₂ are held stationary because interlocked ring gear R₁ and sun gear S₁ are held stationary by brake B₁. Under this condition, ring gear R₃ rotates in the same direction as sun gear S₃ (input shaft 32), but at a reduced speed. This reduced rotation of ring gear R₃ is transmitted to carrier C₂. Ring gear R₂, then, rotates in the same direction as carrier C₂ does at an increased speed because sun gear S₂ is held stationary. This rotation of ring gear R₂ is transmitted to output shaft 34.

From the preceding statement, it will be apparent that there is no rotary elements which will rotate faster than input shaft 32 does.

3rd Speed

For third speed, the clutch K₃ is engaged and clutch K₂ engaged. Under this condition a direct drive is obtained because all gearsets 10, 12 and 20 rotate as a unit.

4th Speed (Over Drive)

For fourth speed (over drive), the clutch K₂ is engaged and brake B₁ applied and a power is transmitted from sun gear S₃ to ring gear R₂ through ring gear R₃ and carrier C₂ because sun gear S₂ is held stationary and carrier C₃ rotates in the same direction as, but at a reduced speed, sun gear S₃. Since sun gear S₁ is held stationary, rotation of input shaft delivered to ring gear R₁ through clutch K₂ is transmitted to carrier C₁ and then carriers C₁ and C₃ rotate in the same direction as input shaft 32 but at a reduced speed. Since carrier C₃ rotates in the same direction as sun gear S₃ but at a reduced speed, ring gear R₃ and carrier C₂ rotate in the same direction. Since sun gear S₂ is held stationary, ring gear R₂ rotates in the same direction as carrier C₂ but at an increased speed. Therefore, suitably selecting the number of teeth of each rotary elements of gearsets 10, 12 and 20, an overdrive can be obtained.

From the preceding statement it is apparent that there is no rotary element which will rotate faster than output shaft 34.

Rev.

For reverse, the clutch K₁ is engaged and brake B₂ applied. Under this condition, since sun gear S₃ rotates as input shaft 32 and carrier C₂ is held stationary, ring gear R₂ rotate in the opposite direction to sun gear S₂ and at a reduced speed.

The sequence for engagement and disengagement or release of the various clutches and brakes in the transmission of FIG. 1 is illustrated in the following Table. The gear ratios are calculated on the assumption that a₁ = a₂ = a₃ = 0.45, where: a₁ is the ratio of the number of teeth of the sun gear S₁ to that of the ring gear R₁ in the first basic planetary gearset 10; a₂ the ratio of the number of teeth of the sun gear S₂ to that of the ring gear R₂ in the second basic planetary gearset 12; and a₃ the ratio of the number of teeth of the sun gear S₃ to that of the ring gear R₃ in the dual intermeshed pinion planetary gearset 20.

In the following Table legend X indicates the condition when a particular friction member is engaged or applied.

                  Table                                                            ______________________________________                                                                                    Gear                                K.sub.1  K.sub.2                                                                              K.sub.3                                                                              B.sub.1                                                                            B.sub.2           Ratio                               ______________________________________                                         1st speed          X       X                                                                                    ##STR1##    2.72                              2nd speed          X   X                                                                                        ##STR2##    1.53                              3rd          X     X            1            1.00                              speed                                                                          4th speed    X         X                                                                                        ##STR3##    0.83                              Rev.   X                   X                                                                                    ##STR4##    2.22                              ______________________________________                                    

Referring to FIG. 4 embodiment, this embodiment differs from first embodiment only in that, instead of the third clutch K₃ in the first embodiment, a third clutch K'₃ is provided and adapted to connect ring gear R₁ to carrier C₁.

Referring to FIG. 5 embodiment, this embodiment differs from the first embodiment only in that, instead of the third clutch K₃ in the first embodiment a third clutch K"₃ is provided and adapted to connect carrier C₁ to sun gear S₁ through shaft 18.

The four-speed transmission constructed as described in the preceding statements has the following advantages:

(1) Since three planetary gearsets, three clutches and two brakes are appropriately combined, the optimum gear ratios for use with automotive vehicles, particularly passenger cars, are obtained by engaging two of the clutches and brakes.

(2) Since an over drive is provided, good fuel economy and silent operation of an automotive vehicle are accomplished because vehicle operation with low engine speed is possible.

(3) Since during all forward speeds, there is no rotary element which rotates faster than an input shaft or an output shaft, the overload on shafts rotatably journaling rotary elements and rattle thereof are eliminated. Although there is rotary element (ring gear R₁) which rotates faster than input shaft during reverse, it is not a problem because engine speed can be lowered. 

What is claimed is:
 1. A change-speed transmission, comprising:a first basic planetary gearset having three rotary elements which are a sun gear, a carrier and a ring gear; a second basic planetary gearset which has a sun gear, a carrier and a ring gear; a dual intermeshed planet pinion planetary gearset which has a sun gear, a carrier and a ring gear; said sun gears of said first and second basic planetary gearsets being connected with each other for simultaneous rotation; an input shaft; an output shaft; said carriers of said first basic planetary gearset and said dual intermeshed planet pinion planetary gearset being connected with each other for simultaneous rotation; said carrier of said second basic planetary gearset and said ring gear of said dual intermeshed planet pinion planetary gearset being connected with each other for simultaneous rotation; said sun gear of said dual intermeshed planet pinion planetary gearset being connected with said input shaft for simultaneous rotation therewith; said ring gear of said second basic planetary gearset being connected with said output shaft; first clutch means for connecting said sun gears of said first and second basic planetary gearsets with said input shaft; second clutch means for connecting said ring gear of said first basic planetary gearset with said input shaft; third clutch means for connecting two of said three rotary elements of said first basic planetary gearset together; first brake means for braking said sun gears of said first and second basic planetary gearsets; and second brake means for braking said carrier of said second basic planetary gearset and said ring gear of said dual intermeshed planet pinion planetary gearset.
 2. A change-speed transmission as claimed in claim 1, in which said ring gear of said first basic planetary gearset and said sun gear thereof are connectable by said third clutch means.
 3. A change-speed transmission as claimed in claim 1, in which said ring gear of said first basic planetary gearset and said carrier thereof are connectable by said third clutch means.
 4. A change-speed transmission as claimed in claim 1, in which said carrier of said first basic planetary gearset and said sun gear thereof are connectable by said third clutch means. 